Nuclear Data Testing

Calculations of Reflected Fast Critical Assemblies and Comparison with Experirhentii Morris E. Battat, TTumas J, Mirons (LASL) 

THOMAS J. HIRONS and MORRIS E. BATTAT, Calculations of Fast Critical Assemblies Using LASL and ENDF/B Version-n Data, Trans, Am. Nucl. Soc., 14, 348 (1971) and LA-DC-12369, Los Alamos Scientific Laboratory (1971). 

HANSEN and H. C. PAXTON, Reevaluated Critical Salifications of Some Los Alamos Fast-NeutrOn Systems, LA-4208, Lbs Alamos Scientifie Laboratory (1969). 

CREMER, R. E. HUNTER, J.-J. H. BERLUN, and V. R. WDRLTON, Conq rison of Calculations with Integral Ejqperiments for Plutonium and Uranium Critical AssembUes, LA-3529, Los Alamos Scientific Laboratory (1969). 

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The Cross-Section Evaluation Working Group (CSEWG) Thermal Data Testing Benchmarks set provides a compilation of experiments most frequently used in the United States for integral nuclear data testing activities. This set includes ... 

Eisenberg et al. (1975) developed estimates of fatalities due to thermal radiation damage using data and correlations from nuclear weapons testing. The probability of fatality was found to be generally proportional to the product where t is the radiation duration and 7 is the radiation intensity. Table 6.7 shows the data used to develop estimates of fatalities from thermal radiation data. 

The earliest tables were compiled from data collected from nuclear weapon tests, in which very high yield devices produced sharp-peaked shock waves with long durations for the positive phase. However, these data are used for other types of blast waves as well. Caution should be exercised in application of these simple criteria to buildings or structures, especially for vapor cloud explosions, which can produce blast waves with totally different shapes. Application of criteria from nuclear tests can, in many cases, result in overestimation of structural damage. 

A mass of evidence seems to confirm that the mixing rate of radiocarbon in the atmosphere is rapid, and that with respect to its radiocarbon content the atmosphere can be considered as a homogeneous entirety. The contamination of samples with matter from an extraneous source can nevertheless invalidate this assumption. Two types of contamination can be differentiated physicochemical contamination and mechanical intrusion. There are two forms of physicochemical contamination. One is due to the dilution of the concentration of radiocarbon in the atmosphere by very old carbon, practically depleted of radiocarbon, released by the combustion of fossil fuel, such as coal and oil. The other is by the contamination with radiocarbon produced by nuclear bomb tests during the 1950s and later in the twentieth century. The uncertainties introduced by these forms of contamination complicate the interpretation of data obtained by the radiocarbon dating method and restrict its accuracy and the effective time range of dating. 

Figure 2. Decrease of muscle cesium-137 concentrations in range cattle following the cessation of atmospheric nuclear weapons testing. Dashed line indicates the regression equation calculated only on 1959 and I960 data.

The half-period for decrease of muscle cesium-137 concentration in NTS animals after the cessation of atmospheric nuclear weapons testing in 1959 appears anomalous (Table I and Figure 2). In addition to being considerably greater (2.3 years) than the other half-periods found, its standard deviation was larger than the value. If one considers only the initial rate of decrease of radiocesium in these muscle samples, one finds a half-period of 0.9 year which is quite consistent with other data. Examination of these data, in comparison with data from liver (Figures 2 and 3), indicates that only muscle decreased its rate of decline in 1960. It should also be noted that the values during 1960 were only about twice the standard error of analysis. Thus, analytical error alone is not an improbable cause of these anomalous values. 

Storm of Nov. 15-17, 1966. The fission product ratio data by nuclear event for this storm are given in Table VII. The storm occurred 18 days after the reported Chinese fourth nuclear weapon test of about 20 lalotons on Oct. 28, 1966 and 190 days after the Chinese third nuclear explosion of about 200 kilotons on May 9, 1966. Also listed is the series of tests conducted by the French in the Southern Hemisphere (near Tahiti) in the time period between these two Chinese tests. A further possible source of fission products was the vented U.S.S.R. underground nuclear explosion of Oct. 27, 1966 (14). The extent of venting is not reported, and contributions to the storm deposition, if any, would appear as part of the fission products from the China-3 explosion. However, the venting process may result in significant fractionation of the fission products. 

Storm of Jan. 20-23, 1967. This storm was characterized by the large (<— 200 kilotons) atmospheric nuclear weapon test of the Chinese (China-5) on Dec. 28, 1966. The pertinent ratio data are given in Table X. The first California storm occurred 25.6 days later. Another possible source of fresh fission products was the reported venting of a U.S.S.R. underground nuclear detonation on Dec. 18, 1966 (17). The prior Chinese and French atmosphere tests occurred 85 to 109 days before the storm date less than 1% of the 140Ba could have come from China-4 and less than 7% from the French tests. 89Sr was still present from the prior tests only 3% was left from the China-3 test of May 9, but the activity levels would still be measurable. 

The significance of radioactivity in water, food, and air has been under particular scrutiny since the advent of nuclear bomb tests and their accompanying radioactive fallout. This scrutiny has resulted in much documented data gathered over the past few decades on the health characteristics of man under various environmental conditions, such as the Denver populace who are subjected to more intense cosmic ray irradiations than the New York City populace the radium dial workers of the 1920,s who have provided data on life spans, general health, and causes of death population s drinking water with varying radium contents persons living... 

Transfer coefficients can also be deduced from statistics of the levels of 90Sr and 137Cs in milk measured during monitoring of the fallout from nuclear weapon tests. This has the advantage over experimental work of taking into account variations in agricultural practices, but introduces complications such as the use of root crops and imported feed for cattle and the uptake by crops from the soil of activity deposited in previous years. UNSCEAR (1977) analysed data from a number of countries, obtained in the years 1958-74, in the form,... 

Cooper et al. (1994) have reported re-suspension studies on soils contaminated with plutonium during nuclear weapons tests by use of a mechanical dust-raising apparatus. Airborne dust was analysed in terms of mass and Am activities for particle sizes less than 7 pm. The AMAD was determined as 4.8-6 pm for re-suspended soil. Also, surface soil was characterised in the laboratory by means of sieving and microparticle classification, yielding mass and "Am activity distribution with respect to size. Data indicate the granularity of plutonium contamination at both major and minor trial sites. Depth profile analyses for undisturbed areas demonstrate that most (74% on average) of the americium and plutonium activity is found in the top 10 mm of soil. Plutonium and americium activities were found to be enhanced in the inhalable fraction over their values in the total soil, and the enhancement factors were similar in re-suspended dust and surface soil. Observed enhancement factors ranged from 3.7 to 32.5. 

The IAEA campaign corroborated the extensive data already available and provided additional scientific information. The activity concentrations of radionuclides in the terrestrial and aquatic environments are generally low and comparable with reported concentrations of the same radionuclides at similar atolls where no nuclear weapon testing took place. 

The International Atomic Energy Agency organized a series of interlaboratory comparisons for calibration purposes. Those completed so far include two seawater, one seaweed Fucus vesiculosus), and one sediment sample. These materials were contaminated in nuclear waste disposal situations and, in consequence, contain transuranic elements in concentrations much higher than those found in samples contaminated by global fallout of nuclear weapons testing debris. Nevertheless, the data speak directly to questions of calibration of detectors and yield... 

Before natural tritium could be fully exploited for studies of natural water systems, tritium from anthropogenic sources (mainly nuclear weapon tests) was added to the atmosphere in considerable amounts. By the mid 1960s the natural background of tritium in precipitation was practically masked by so-called bomb tritium (e.g., Weiss et al. 1979 Fig. 1). For the past 4 to 5 decades, bomb tritium severely limited the use of natural tritium as a tracer because only few uncontaminated tritium data are available from the pre-bomb era. However, bomb tritium offered a new tool for studies of water movement in natural system. It is equivalent to a dye that was introduced into the environment on a global scale at a relatively well-known rate. Most of the bomb tritium was added to the environment in three pulses during 1954, 1958-1959 and, predominantly, 1963. 

An overview of relativistic state-of-the-art calculations on electric field gradients (EFG) in atoms and molecules neccessary for the determination of nuclear quadrupole moments (NQM) is presented. Especially for heavy elements four-component calculations are the method of choice due to the strong weighting of the core region by the EFG operator and the concomitant importance of relativity. Accurate nuclear data are required for testing and verification of the various nuclear models in theoretical nuclear physics and this field represents an illustrative example of how electronic structure theory and theoretical physics can fruitfully interplay. Basic atomic and molecular experimental techniques for the determination of the magnetic and electric hyperfine constants A and B axe briefly discussed in order to provide the reader with some background information in this field. 

In some recent work on persistently only pp data are considered [31, 32]. Since some potentials fit the pp data much better than np (cf. Table 1), it may be tempting to do so (for reasons that, however, have little to do with physics), pp states exist only for T = 1 and, thus, a comparison with the pp data tests only the T = 1 potential. Confrontation with np data tests both T = and T = 0 and, thus, is a much more comprehensive test of a potential. In fact, the problems of some potentials shown in Figs. 2 and 3 are due to T = 0 states and, thus, are missed when only pp is considered. Moreover, in nuclear structure calculations, typically both the T = 0 and the T = 1 potential is needed. In nuclear structure, the T = 0 states are in general as important as the T = 1 states (in fact, one may well argue that the T = 0 states are even more crucial since the very important states is T = 0). 

AOYAMA, T., ITO, C., Integral Test on Activation Cross Section of Tag Gas Nuclides Using Fast Neutron Spectrum Fields, Proc. Int. Conf. on Nuclear Data (ND2001), Ibaraki, Japan, 7-12 October 2001, JAERI, published as Journal of Nuclear Science and Technology, Supplement 2 (2002). 

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